1. Field of the Invention
The present invention relates to a structure for holding a brush of a motor, which brush is radially pressed against a commutator.
2. Background Information
Generally, respective brushes of a direct current motor are so arrnaged as to be pressed against a commutator in radial directions thereof, or directions perpendicular to the axis of the commutator.
In this case, each brush there is play or fine movements due to a clearance between a brush holder and the brush to cause the occurrence of noise at the time when the motor rotates. Therefore, a structure for biasing each brush in a tangential direction of a commutator by means of a resilient body to press the brush against the interior of a holder has been proposed in Japanese Utility Model Application Laid Open No. SHO 61-62547. Also, having been proposed in Japanese Utility Model Application Laid Open No. SHO 60-82966 is a structure in which each brush holder is disposed close to the outer periphery of a commutator as much as possible to stabilize a holding force for a brush.
In these motors, however, because pressing forces for the respective brushes vary as the brushes wear, it is impossible to always give the respective brushes uniform pressing forces.
Moreover, in these motors, consideration is given to only the play of the respective brushes occurring in the radial directions of the commutators, and the play of the respective brushes occurring in the axial directions of the commutators has not been considered. Hitherto, therefore, in order to eliminate the play of each brush which occurs in the axial directions of a commutator, a structure for inclining the brush within a plane along the axial direction of the commutator has been proposed in Japanese Utility Model Application Laid Open No. SHO 58-112075. However, even with this motor, a biasing force for pressing the brush varies as the brush wears, and it is therefore impossible to ensure elimination of the play of the brush.